1. Field of the Invention
This invention relates to new and useful improvements in abrasive blasting apparatus for treatment of surfaces and more particularly to a mobile abrasive blasting apparatus for surface treatment.
2. Brief Description of the Prior Art
The prior art discloses a variety of machines for treating surfaces by impingement of particulate abrasive material. There are a large number of patents and other literature which are concerned with sand blasting devices and also shot blasting and other abrasive blasting apparatus.
Pawlson U.S. Pat. No. 3,034,262 discloses a resurfacing and finishing machine for use in treating surfaces of various shapes, whether horizontal or vertical, in which particulate abrasive material was introduced through an inlet at an angle and impinged against a surface at an angle by means of a throwing wheel and recovered and recirculated.
Mabille U.S. Pat. No. 3,380,196 discloses a mobile surface treating apparatus including a centrifugal impeller for impelling a concentrated stream of particulate material against the surface to be treated and includes means for collecting the particulate material after impingement on the surface.
Goff U.S. Pat. No. 3,691,689 discloses a mobile continuously operable abrasive surface cleaning apparatus which utilizes a rotating brush for recovery of the abrasive particles.
Leliaert U.S. Pat. No. 3,858,359 discloses a mobile apparatus for the surface treatment with particulate material thrown against the surface at high speed. The particulate material used is ferromagnetic and elements are provided for removal of the particulate material from the treated surface and a magnetic drum and conveyor for attracting the ferromagnetic material and conveying it for subsequent reuse.
Snyder U.S. Pat. No. 3,877,175 discloses a mobile apparatus for surface treatment with a particulate material thrown onto the surface at high speed. The apparatus is characterized by its use of a suction nozzle at the rear and a blower nozzle at the forward end of the apparatus to project a stream onto the surface for sweeping particulate material and waste in advance of the suction nozzle.
Goto U.S. Pat. No. 3,906,673 discloses a portable abrasive cleaning machine having a motor driven impeller for discharging an abrasive material against the surface to be treated. Air currents from a pressurized air source are employed to power the motor to feed the abrasive agent to the impeller to convey the abrasive agent particles back to the container and to separate the abrasive agent from the particles discharged into a bag filter.
Leliaert U.S. Pat. No. 3,934,373 discloses a portable apparatus for surface treatment with particulate material thrown against the surface at high velocity by a rotating wheel. The apparatus includes features for removing the particulate material and debris from the surface and particularly including a magnetic drum for attracting ferromagnetic material, a vacuum pack-up for removing nonmagnetic material an air jets for position and lifting the material to increase the efficiency of the recovery process.
Goff U.S. Pat. No. 3,977,128 discloses an improved abrasive throwing machine for projecting abrasive particles at an inclined angle relative to the surface to be treated and including rotary brushes for cleaning the surface and assisting in recovery of spent abrasive particles.
Shigyo U.S. Pat. No. 4,020,597 discloses a mobile floor cleaning and polishing apparatus which has a centrifugal projector for impelling abrasive particles against the surface and a magnetic drum for attracting and collecting the used particles and a vacuum suction system for recovering other particles.
Bergh U.S. Pat. No. 4,052,820 discloses a portable apparatus for treatment of surfaces having a centrifugal wheel for projecting abrasive particles onto the surface at an angle of 30.degree. to 80.degree. from the surface. A rebound corridor extending angularly upward and incorporating a paddle wheel carries the spent particles to a level above the hopper and the particles rebound and are collected in a reservoir and separated from particulate surface material.
Leliaert U.S. Pat. No. 4,080,760 discloses a portable or mobile surface treating apparatus having an abrasive particle throwing wheel and magnets for assisting in separating ferromagnetic particulate material. The nonmagnetic material is blown free and conveyed to a dust collector.
VanFossen U.S. Pat. No. 4,202,182 discloses an abrasive blast treating apparatus which is mobile and has a recovery system in which spent abrasive particles are separated from dust and dirt and collected in a reservoir and fed back to the abrasive throwing wheel.
The apparatus shown in the various prior art references cited is subject to a variety of problems. In many cases the apparatus is not sufficiently flexible for use in the treating of irregular surfaces. In other cases the separation of particulate abrasive from particulate debris removed from the surface is incomplete. In other cases there is a residue of particulate abrasive material left on the surface which is not recovered. Also, there is a tendency for the abrasive particles to rebound in the collection chambers and cause problems in separation and recovery.